diff --git a/CONTEXT.md b/CONTEXT.md
index 32ca2f1c5..3cdc8e2d0 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -85,6 +85,9 @@ Module owning validation for Installer Migration Module records and planned acti
 ### Skill Surface Budget Module
 Module owning which skills and agents are written to runtime config directories at install time (Phase 1) and at runtime via cluster-level toggles (Phase 2). Phase 1: `get-shit-done/bin/lib/install-profiles.cjs` defines named profiles (`core`, `standard`, `full`), computes transitive closure over `requires:` frontmatter, stages skills/agents to runtime config dirs, and persists the chosen profile in a `.gsd-profile` marker. Profile resolution precedence: explicit `--profile=` flag > `.gsd-profile` marker > `full`. `--minimal`/`--core-only` are back-compat aliases for `--profile=core`. Phase 2: `get-shit-done/bin/lib/surface.cjs` implements the `/gsd:surface` slash command for cluster-level enable/disable without reinstall; cluster definitions live in `get-shit-done/bin/lib/clusters.cjs`; per-runtime state persists in `<runtimeConfigDir>/.gsd-surface.json` independent from the `.gsd-profile` marker. See ADR-0011.
 
+### Runtime Artifact Layout Module
+Module owning the per-runtime mapping from artifact kind to filesystem placement. ADR-3660 defines the typed `kinds` per runtime (`commands`, `agents`, `skills`) with destination subpath, prefix, and stage adapter (with per-runtime converters in `bin/install.js`: `convertClaudeCommandToClaudeSkill`, `…CodexSkill`, `…CopilotSkill`, `…AntigravitySkill`). Phase 1 applies this seam to the Runtime Surface Module (`surface.cjs:applySurface`). Phase 2 is planned to migrate install/uninstall in `bin/install.js` so all lifecycle sites iterate one shared layout table instead of re-encoding runtime layout logic. This design is intended to remove the #3659 class of omissions. Migrations remain under the Installer Migration Module (ADR-0008). See ADR-3660.
+
 ### MVP Mode
 Phase-level planning mode that frames work as a vertical slice (UI → API → DB) of one user-visible capability instead of horizontal layers. Resolved at workflow init via the precedence chain: `--mvp` CLI flag → ROADMAP.md `**Mode:** mvp` field → `workflow.mvp_mode` config → false. All-or-nothing per phase (PRD #2826 Q1). Surfaced as `MVP_MODE=true|false` to the planner, executor, verifier, and discovery surfaces (progress, stats, graphify). Canonical parser: `roadmap.cjs` `**Mode:**` field; canonical resolution chain documented in `workflows/plan-phase.md`. Concept index: `references/mvp-concepts.md`.
 
diff --git a/docs/adr/3660-runtime-artifact-layout-module.md b/docs/adr/3660-runtime-artifact-layout-module.md
new file mode 100644
index 000000000..541610710
--- /dev/null
+++ b/docs/adr/3660-runtime-artifact-layout-module.md
@@ -0,0 +1,136 @@
+# Runtime Artifact Layout Module owns per-runtime artifact placement
+
+- **Status:** Proposed
+- **Date:** 2026-05-17
+- **Issue:** #3660
+
+The **Runtime Surface Module** (`get-shit-done/bin/lib/surface.cjs`, introduced by ADR-0011 Phase 2) re-materializes a resolved Skill Surface profile to disk via `applySurface`. It currently hardcodes two artifact kinds (`commands`, `agents`) and re-derives their source directories via `_findInstallSource` / `_findAgentsSource` walk-up heuristics. The install and uninstall pipelines in `bin/install.js` each encode the same per-runtime artifact layout independently across ~14 install sites and ~6 uninstall sites. Bug #3659 surfaced the resulting drift: `applySurface` omits the `skills` kind for runtimes whose canonical layout is `skills/gsd-<stem>/SKILL.md`, so `gsd-surface profile <name>` leaves ~67 skill directories on disk under the install-time profile's footprint when the resolved profile should have pruned them — roughly 2.7k tokens per session on a measured workstation.
+
+The root problem is the absence of a typed seam for "where does runtime R put artifact kind K." Three lifecycle sites (install, uninstall, surface) each independently encode this knowledge and drift independently.
+
+## Decision
+
+- Add a **Runtime Artifact Layout Module** at `get-shit-done/bin/lib/runtime-artifact-layout.cjs` as the single owner of the per-runtime artifact-placement table.
+- The module requires `runtime-homes.cjs` for the canonical runtime enum and global config-dir resolution. It adds the artifact-kind axis on top.
+- Expose `resolveRuntimeArtifactLayout(runtime, configDir) → Layout`. The returned `Layout` is a plain typed object — `{ runtime, configDir, kinds: ArtifactKind[] }` — with no I/O on resolution.
+- Each `ArtifactKind` is `{ kind: 'commands'|'agents'|'skills', destSubpath, prefix, stage }`. `stage` is a function `(resolvedProfile) → stagedDir` that closes over the per-runtime converter where one is needed (e.g. `convertClaudeCommandToClaudeSkill` for the `skills` kind on Claude global).
+- The `kinds` array is empty for runtimes with no GSD surface (a hypothetical future runtime with no integration). The `skills` kind is **absent** for runtimes that don't materialize skill directories (Cline; Gemini today). The `commands` kind is **absent** for runtimes that consume only the skills/agents layout (Claude global, Codex, etc.).
+- Per-runtime quirks live in the layout's record fields, not in caller branches:
+  - **Hermes**: `{ kind: 'skills', destSubpath: 'skills/gsd', prefix: '' }` — preserves the nested namespace from #2841.
+  - **Cline**: `kinds: [ { kind: 'commands', … } ]` — no skills kind in the array.
+  - **Gemini**: `kinds: [ { kind: 'commands', destSubpath: 'commands/gsd', prefix: 'gsd-' } ]` — no agents, no skills.
+- `applySurface` migrates from `(runtimeConfigDir, commandsDir, agentsDir, manifest, clusterMap)` to `(runtimeConfigDir, layout, manifest, clusterMap)`. Body collapses to `for (const kind of layout.kinds) _syncGsdDir(kind.stage(resolved), path.join(layout.configDir, kind.destSubpath), kind.kind)`.
+- `_findInstallSource` and `_findAgentsSource` in `surface.cjs` are removed. The layout owns source resolution.
+- Phase 2 (separate PR): install and uninstall paths in `bin/install.js` migrate to iterate `layout.kinds`. Per-runtime if/else branches for skill-directory creation/removal collapse to one layout-driven loop per pipeline.
+- Legacy-layout migrations (`bin/install.js:6710`/`:8402` for the pre-nested `skills/gsd-*/` flat layout; `migrateLegacyDevPreferencesToSkill` for #2973) remain inside the Installer Migration Module (ADR-0008) and run **before** layout-driven copy. The layout module describes only the current canonical target — no historical kinds.
+
+## Initial Scope
+
+Phase 1 should land the module and one consumer (the bug-#3659 fix):
+
+1. New `get-shit-done/bin/lib/runtime-artifact-layout.cjs` — `resolveRuntimeArtifactLayout`, the typed `Layout`/`ArtifactKind` shapes, and the runtime table covering every runtime currently enumerated in `runtime-homes.cjs`.
+2. `surface.cjs:applySurface` migrates to layout-driven iteration. `_findInstallSource` and `_findAgentsSource` deleted. The `skills` kind is now iterated alongside `commands` and `agents` — bug #3659 closed.
+3. `commands/gsd/surface.md` and `tests/surface-apply.test.cjs` updated to construct + pass `Layout` values.
+4. New `tests/runtime-artifact-layout-*.test.cjs` covering:
+   - Per-runtime fixture table: each runtime maps to the expected `kinds[]` shape.
+   - Hermes `skills/gsd` nested case.
+   - Cline / Gemini "kind absent" cases.
+   - Source-root resolution (replacing the existing `surface.cjs` walk-up tests).
+5. Address the adjacent `readSurface` partial-field silent-null bug noted in #3659 — out of scope here; track as a separate `confirmed-bug` ticket.
+
+Phase 1 should **not**:
+
+- Migrate the install/uninstall pipelines in `bin/install.js` in the same PR. That's a separate enhancement issue — same seam, larger blast radius. The layout module is dual-consumable from the start; converting `bin/install.js` is a sequenced follow-up.
+- Move the per-runtime skill converters (`convertClaudeCommandToClaudeSkill`, etc.). They survive at their current file location as the stage adapters; the layout module references them. A future ADR may consolidate them into a Skill Conversion Module if a second consumer emerges.
+
+## Migration Inventory
+
+### New file
+- `get-shit-done/bin/lib/runtime-artifact-layout.cjs` — module body + runtime layout table.
+
+### Files modified (Phase 1)
+- `get-shit-done/bin/lib/surface.cjs` — `applySurface` signature change; `_findInstallSource` + `_findAgentsSource` removal.
+- `commands/gsd/surface.md` — runbook updates the 3 sites that call `applySurface` to first call `resolveRuntimeArtifactLayout`.
+- `tests/surface-apply.test.cjs` — 5 call sites pass `layout` instead of `commandsDir, agentsDir`.
+
+### Files modified (Phase 2 — separate PR / separate issue)
+- `bin/install.js` — install path: 4 per-runtime skill-stage blocks collapse to one layout-driven loop.
+- `bin/install.js` — uninstall path: 6 per-runtime skill-removal blocks collapse to one layout-driven loop.
+- Estimated reduction: ~250 lines.
+
+### Files not touched
+- `runtime-homes.cjs` — its narrow contract (runtime → global config dir / skills base) stays. The layout module is its sibling.
+- `install-profiles.cjs` — `stageSkillsForProfile`, `stageAgentsForProfile` remain. The layout module's `kinds[i].stage` closures call them.
+- The four skill converters at `bin/install.js:1622/1681/1792/2534` — remain in place; layout closures reference them.
+
+## Interface sketch
+
+```js
+// runtime-artifact-layout.cjs
+
+/**
+ * @typedef {Object} ArtifactKind
+ * @property {'commands'|'agents'|'skills'} kind
+ * @property {string} destSubpath              joined to layout.configDir
+ * @property {string} prefix                   'gsd-' or '' (Hermes nested case)
+ * @property {(resolved) => string} stage      returns staged dir path
+ */
+
+/**
+ * @typedef {Object} Layout
+ * @property {string} runtime                  canonical enum from runtime-homes.cjs
+ * @property {string} configDir                caller-supplied (local or global scope)
+ * @property {ArtifactKind[]} kinds            empty array = runtime has no gsd-* surface
+ */
+
+function resolveRuntimeArtifactLayout(runtime, configDir) { … }
+```
+
+Call-site shape:
+
+```js
+// commands/gsd/surface.md (runbook), tests/surface-apply.test.cjs, future install/uninstall
+const layout = resolveRuntimeArtifactLayout(runtime, runtimeConfigDir);
+applySurface(runtimeConfigDir, layout, manifest, CLUSTERS);
+```
+
+`applySurface` body after migration:
+
+```js
+function applySurface(runtimeConfigDir, layout, manifest, clusterMap) {
+  const resolved = resolveSurface(runtimeConfigDir, manifest, clusterMap);
+  for (const kind of layout.kinds) {
+    const staged = kind.stage(resolved);
+    const dest = path.join(layout.configDir, kind.destSubpath);
+    if (fs.existsSync(dest)) _syncGsdDir(staged, dest, kind.kind);
+  }
+}
+```
+
+## Consequences
+
+- Bug #3659 becomes a fixture-table omission, not a forgotten if/else block. The layout-table test asserts every runtime's `kinds[]` shape — forgetting the `skills` kind on Claude global would fail there.
+- The cross-runtime test matrix collapses from `N runtimes × 3 lifecycle verbs × 3 kinds` (today: ~120 implicit assertion pairs) to `N (layout table) + 3 (one per lifecycle verb iterating layout.kinds)`.
+- Adding a new runtime (recent example: Grok via commit `05316369`) becomes one row in the layout table plus one fixture row in the test. The three lifecycle verbs pick it up automatically.
+- The four per-runtime skill converters become canonical **adapters** at the artifact-kind seam. Their existence is no longer accidental — they're the seam's content.
+- `surface.cjs` shrinks (`_findInstallSource` + `_findAgentsSource` removed). The walk-up heuristics — which were only ever-incidentally correct — are replaced by an explicit table.
+- Phase 2 (install/uninstall migration) shrinks `bin/install.js` by ~250 lines and removes a recurring class of bug: a new runtime added by a contributor who forgets to wire it through every install/uninstall branch.
+- Future architecture reviews should treat per-runtime artifact-placement knowledge added outside `runtime-artifact-layout.cjs` as drift, parallel to how ADR-0011 made out-of-seam skill staging drift.
+- The Skill Surface Budget Module's leverage (typed sets of `{ skills, agents }`) now extends all the way to disk through one seam rather than three independent re-materializations.
+
+## Open questions
+
+- Whether the `skills` kind's `stage` closure should accept the per-runtime converter as a parameter (preserving converter-as-pure-function purity) or import it directly. Implementation detail — settle in the PR.
+- Whether the layout module should expose a `listKinds(runtime)` introspection helper for status/diagnostics surfaces, or keep `Layout` as the only public type. Lean toward a single public type; add helpers only when a second consumer needs them.
+- Whether Phase 2 (install/uninstall migration in `bin/install.js`) should land as a single follow-up PR or be split per pipeline. Lean toward single PR — the install and uninstall sides share the runtime branch structure and migrating only one introduces a temporary asymmetry inverse to today's.
+- The adjacent `readSurface` partial-field silent-null fallback in `surface.cjs:55-75` (also flagged in #3659) is **out of scope here** — track separately. It's an independent shallow interface in the same module, not a runtime-layout concern.
+
+## References
+
+- Confirmed bug: `#3659` — `applySurface` doesn't prune `~/.claude/skills/gsd-*/` dirs
+- See `0011-skill-surface-budget-module.md` — the Runtime Surface Module this seam serves
+- See `0008-installer-migration-module.md` — legacy-layout migrations stay there
+- See `0005-sdk-architecture-seam-map.md` — the seam map this module joins
+- Existing canonical sibling: `get-shit-done/bin/lib/runtime-homes.cjs`
+- Per-runtime skill converters this module references: `bin/install.js:1622` (Copilot), `:1681` (Claude), `:1792` (Antigravity), `:2534` (Codex)
+- Hermes nested-skills layout rationale: `#2841`
diff --git a/docs/adr/README.md b/docs/adr/README.md
index 50b73d4ed..1ef8c2be7 100644
--- a/docs/adr/README.md
+++ b/docs/adr/README.md
@@ -45,6 +45,7 @@ See **[CONTRIBUTING.md — "Proposing an ADR or PRD"](../../CONTRIBUTING.md#prop
 | [0011-review-default-reviewers.md](0011-review-default-reviewers.md) | Review default-reviewers selection policy for /gsd:review | Accepted |
 | [0011-review-default-reviewers-prd.md](0011-review-default-reviewers-prd.md) | PRD for review.default_reviewers feature (#3464) | Reference |
 | [3524-cjs-sdk-hard-seam.md](3524-cjs-sdk-hard-seam.md) | CJS↔SDK hard seam — single canonical owner per responsibility (#3524) | Proposed |
+| [3660-runtime-artifact-layout-module.md](3660-runtime-artifact-layout-module.md) | Runtime Artifact Layout Module owns per-runtime artifact placement | Proposed |
 
 ## Seam map